Retired businessman has been held in America since February charged with conspiring to sell batteries for Iranian missiles

A plea deal between extradited Briton Christopher Tappin and US prosecutors is the beginning of his “swift and safe return” to the UK, his wife said today.

The retired British businessman is expected to reach a deal with prosecutors on Thursday over charges of conspiring to sell batteries for Iranian missiles.

His wife Elaine said “however upsetting” a plea deal was, it marked the beginning of his “swift and safe return” to the UK.

Mrs Tappin, who has chronic Churg-Strauss syndrome, said: "From the moment Chris was put on a plane all we ever wanted was his swift and safe return.

“However upsetting, this is the beginning of that process.

“It would be inappropriate to comment further whilst the Court has yet to establish Chris’ fate.”

Tappin, 65, of Orpington, Kent, is on bail and will appear in court in El Paso, Texas, on Thursday to hear prosecutors set out the terms of his plea bargain, a family spokeswoman said.

If the terms are agreed by senior US district judge David Briones, it is likely to be several weeks before he is sentenced.

He faces up to 35 years in jail, but this is likely to be significantly reduced under the terms of any plea deal.

No details of the terms have been released, but other Britons who have been extradited said they had no chance of being cleared once sent to the US as the plea bargaining system empowers prosecutors as “judge, jury and executioner”.

David Bermingham, who was one of three bankers jailed for 37 months over an Enron-related fraud in a deal with US prosecutors in 2008, said in March that no sane defendant would risk dozens of years in jail when a plea bargain could enable them to be home within months.

Plea bargaining is common in the US, with defendants often able to secure a more lenient sentence if they admit an offence and co-operate with prosecutors, rather than contest the charges in a trial.

But the system, and the pressure it places on defendants, leaves those extradited to the US from the UK with little choice but to accept a deal if they want to return to their families at home, Bermingham, of Goring, south Oxfordshire, claimed in March.

“A prosecutor can now effectively be judge, jury and executioner,” he said.

“He can say, ’I’m going to charge you with 98 different counts, each carrying a five or 10 year maximum sentence, and potentially you could be sentenced to literally the rest of your life in prison’.

“And there’s no parole. There’s no two ways about it.

“A prosecutor can threaten a defendant with the rest of his life in prison. However if you are willing to plead guilty, 30 years becomes five years.

“If you are then co-operating and willing to give evidence against others, five years becomes two.”

US prosecutors often quote maximum sentences, rather than the most likely jail term, for each offence, in part to act as a deterrent to others.

Tappin’s case followed an investigation which started in 2005 when US agents asked technology providers about buyers who might have raised red flags.

Those customers were then approached by undercover companies set up by government agencies.

Briton Robert Gibson, an associate of Tappin who agreed to co-operate, was jailed for 24 months after pleading guilty to conspiracy to export defence articles.

Gibson provided customs agents with about 16,000 computer files and emails indicating that he and Tappin had long-standing commercial ties with Iranian customers.

American Robert Caldwell was also found guilty of aiding and abetting the illegal transport of defence articles and served 20 months in prison.